In recent years, the characteristics and performance of CMOS image sensors and Charge Coupled Device (CCD) image sensors, among others, have improved, and demand for these image sensors has grown accordingly. Turning to FIG. 1, a conventional CMOS image sensor 100 can be seen. The CMOS sensor 100 generally comprises an array 102 of pixels 106-11 through 106-MN and interface circuitry 104. The interface circuitry 104 can then generate output signals N and NS. Generally, these signals N and NS are processed by circuitry to generate digital signals.
An example of a conventional processing circuit can be seen in FIG. 2. Circuit 200 signals N and NS from pixels 106 (which can be any of pixels 106-11 to 106-MN and which are read sequentially or in parallel). An summing circuit 202 calculates the difference between signals NS and S to generate an analog signal S in a so-called a correlated double sampling (CDS) circuit. Signal S is input to analog-to-digital converter (ADC) 204 and converted into digital signal DS. However, circuit 200 has undesirable noise characteristics.